(Applicable to all Allowable Development as identified in Article Five, except Sections 501 and 506) When a Floodplain Use Permit is required pursuant to Section 401, these Development Standards shall apply in all Special Flood Hazard Areas except Zone AE Floodway and Alluvial Fan Administrative Floodway. See additional requirements for specific Flood Hazard Zones in Sections 602 through 618. All standards should be read and applied pertinent to development proposed. A. General
1. Residential homes with a basement are not permitted within the 100-year floodplain.
2. New construction or substantial improvement to any existing structure shall be constructed with methods that minimize flood damage with materials and utilities resistant to flood damage.
3. Dwellings other than mobile/manufactured homes shall have the lowest floor elevated and all utilities, including ductwork, shall be floodproofed up to or above the Regulatory Flood Elevation. See Section 601(G)2.
4. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
5. In order to control erosion and preserve the natural and beneficial functions of the floodplain, removal of vegetation shall be the minimum necessary for the development. 6. Adequate drainage paths around structures on slopes to guide floodwaters around and away
from proposed structures are required.
7. For buildings elevated greater than five (5) feet, enclosures, including breakaway walls, below the Base Flood Elevation are prohibited. Screening and open latticework is not considered an enclosure. Applicant must sign a non-conversion agreement, agreeing not to enclose the area for habitable use.
8. All new construction and substantial improvements that fully enclose areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement, and are subject to flooding, shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. The applicant shall provide a Flood Proofing Certificate by an Arizona Registered Professional Engineer certifying that the flood proofing requirements have been met, or the design shall meet the provisions of Section 601(A)9.
9. Buildings other than dwellings or any type of residence may have the lowest floor below the Regulatory Flood Elevation provided that all of the following conditions are met:
a. They shall be watertight with walls substantially impermeable to the passage of water; and
b. Structural components and utilities, including ductwork shall have the capacity of resisting the effects associated with a base flood; and
c. Designs for meeting these criteria shall be certified on a Flood Proofing Certificate by an Arizona Registered Professional Engineer or the design must meet or exceed the following minimum criteria:
A minimum of two (2) openings, on at least two (2) sides, having a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding shall be provided. The bottom of all openings shall be no higher than one (1) foot above finished grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided they allow the automatic entry and exit of floodwaters. 10. Storage containers (i.e., shipping containers) designed to be watertight with walls
substantially impermeable to the passage of water and the capacity of resisting the effects associated with a base flood shall not be required to have openings as required in Section 601(A)9. Anchoring may be required.
11. When the improvements, modifications, additions, reconstruction or repairs reach the fifty percent (50%) substantial improvement threshold, then the entire structure must be brought into compliance. The value of the improvements, modifications, reconstruction, repair or additions is counted cumulatively for five (5) years to determine whether the substantial improvement threshold has been met.
12. For all new construction and substantial improvements, the building material below the Regulatory Flood Elevation shall be of flood resistant material. Flood-resistant materials include any building product capable of withstanding direct and prolonged contact with floodwaters without sustaining significant damage. Prolonged contact means at least 72 hours, and significant damage is any damage requiring more than low-cost cosmetic repair (such as painting). Additional information can be found in FEMA Technical Bulletins. Materials include, but are not limited to the following:
a. Concrete, concrete block, or glazed brick; b. Clay, concrete, or ceramic tile;
c. Galvanized or stainless steel nails;
d. Indoor-outdoor carpeting with synthetic backing (not fastened down); e. Vinyl, terrazzo, rubber, or vinyl floor covering with waterproof adhesives; f. Metal doors and window frames;
g. Polyester-epoxy paint; h. Stone, slate, or cast stone;
i. Mastic, silicone, or polyurethane formed-in-place flooring. Styrofoam insulation; j. Water resistant glue;
k. Pressure treated (.40 CCA minimum) or naturally decay-resistant lumber, marine grade plywood.
13. All recreation vehicles in accordance with 44 CFR 60.3(C)(14) placed on site will either: a. Be on-site for fewer than 180 consecutive days, and be fully licensed and ready for
highway use. A recreation vehicle is ready for highway use if it is on wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or
b. Meet the permit requirements of Article Four of these Regulations and the elevation and anchoring requirements for manufactured homes in Section 601.
B. Mobile/Manufactured Homes
1. Mobile/manufactured homes including permanently placed recreation vehicles and modular buildings shall be elevated so that the bottom of the structural frame is at or above the Regulatory Flood Elevation and is anchored to prevent flotation, collapse or movement. Methods of anchoring may include, but not be limited to, use of over the top or frame ties to ground or foundation anchors. Specific requirements shall be as follows:
a. Over the top or frame ties shall be provided at each of the four corners of the mobile/manufactured home, with additional ties on each side at intermediate locations; b. Mobile/manufactured homes more than fifty (50) feet long require one (1) additional tie
per side;
c. All components of the anchoring system shall be capable of carrying a force of 4,800 pounds;
d. Adequate surface drainage and access for a hauler are provided;
e. If the mobile/manufactured home is elevated on piers, setbacks shall be sufficient to permit steps; pier foundations shall be placed in stable soil no more than ten (10) feet apart, and reinforcement is provided for piers more than six (6) feet above ground level. A scour analysis may be required when elevating on piers;
f. Any additions to the mobile/manufactured home shall be similarly anchored; and
g. Attached appliances and all utilities, including ductwork, shall be either elevated or floodproofed up to the Regulatory Flood Elevation.
The above requirements do not apply to units in storage, and may be waived by the Floodplain Administrator on a case by case basis for units placed for less than 180 consecutive days that are properly licensed and ready for highway use, or are on jacks or wheels with quick disconnect of utilities and have no permanently attached additions. 2. For all mobile/manufactured home parks and mobile/manufactured home subdivisions, an
evacuation plan indicating alternate vehicular access and escape routes shall be filed with the Maricopa County Department of Emergency Management.
3. A mobile home located in a floodplain prior to August 3, 1985 may be replaced by another mobile home if:
a. The mobile home to be replaced was not damaged by a flood to more than fifty per cent of its value before the flood.
b. The replacement mobile home is elevated so that the bottom of the structural frame or the lowest point of any attached appliances, whichever is lower, is at or above the regulatory flood elevation.
C. Subdivisions
1. All subdivision proposals and other proposed new developments greater than fifty (50) lots or five (5) acres, whichever is the lesser, shall include within such proposals Base Flood Elevation data.
2. All preliminary subdivision proposals shall identify the Special Flood Hazard Area and the elevation of the base flood.
3. All subdivision proposals shall be consistent with the need to minimize flood damage. 4. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical
and water systems located and constructed to minimize flood damage.
5. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.
6. All final subdivision plans will provide the elevation(s) of proposed structure(s) and pads. If the site is filled above the base flood, the final lowest floor and pad elevation shall be certified by a registered professional engineer or surveyor and provided to the Floodplain Administrator.
D. Fill Material
1. Fill material, if used to elevate structures, shall meet all of the following standards:
a. The top of such fill material shall be at no point lower than the Base Flood Elevation. b. Such fill material shall extend at least five (5) feet beyond the walls or supporting frame
of the structure, or as approved by the Floodplain Administrator.
c. Fill material shall be placed and compacted in accordance with the applicable Building Code.
d. Fill material shall not interfere with local drainage or tributary flow of the channel of any watercourse.
2. Fill material proposed in excess of the amount and extent required herein shall be shown by the applicant to have no detrimental effect on the purposes of these Regulations and the amount of fill material shall not be greater than is necessary to achieve the purpose for which it is intended as demonstrated by a plan submitted by the applicant indicating the uses to which the filled land will be put and the final dimensions and extent of the proposed fill material.
3. Adequate erosion protection shall be provided for fill slopes exposed to moving floodwaters (slopes exposed to flows with velocities of up to five (5) feet per second (fps) during the base flood must, at a minimum, be protected by a permanent cover of grass, vines, weeds, or similar vegetation; slopes exposed to flows with velocities greater than five (5) fps during the base flood must, at a minimum, be protected by appropriately designed stone, rock, concrete, or other durable materials).
4. Fill material for purposes other than solid waste landfills shall not include solid waste, wood, or other buoyant materials nor hazardous, toxic or deleterious material and shall be protected as needed against scour and erosion by riprap or other protective measures as approved by the Floodplain Administrator.
E. Garages and Low Cost Accessory Structures 1. Attached Garages
a. A garage attached to a residential structure, constructed with the garage floor slab below the regulatory flood elevation, must be designed to allow for the automatic entry and exit of floodwaters. Areas of the garage below the Regulatory Flood Elevation must be constructed with flood resistant materials.
b. A garage attached to a nonresidential structure must meet the above requirements or be dry floodproofed as required in Section 601(A)9.
c. Applicable Standards in Section 601(A) and (B) shall apply to attached garages. 2. Detached Garages and Accessory Structures
a. An accessory structure used solely for parking (2-car detached garages or smaller) or limited storage (small, low-cost sheds) may be constructed such that its floor is below the regulatory flood elevation, provided the structure is designed and constructed in accordance with the following requirements:
1) Use of the accessory structure must be limited to parking or limited storage;
2) The portions of the accessory structure located below the Regulatory Flood Elevation must be built using flood-resistant materials as identified in 601(A)12; 3) The accessory structure must be adequately anchored to prevent flotation, collapse
and lateral movement;
4) Any mechanical and utility equipment in the accessory structure must be elevated or floodproofed to or above the Regulatory Flood Elevation;
5) The accessory structure must comply with floodplain encroachment provisions in these Regulations; and
6) The accessory structure must be designed to allow for the automatic entry and exit of floodwaters in accordance with Section 601(A)9.
b. Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in these Regulations.
F. Landfills / Extraction of Sand and Gravel and Other Materials
1. Permitted landfills shall be protected against scour, erosion and contamination by and contamination of the 100-year flood event.
2. Extraction of sand and gravel and other materials operations shall meet the requirements of this Article where applicable.
G. Other Requirements
1. Issuance of a Floodplain Use Permit does not exempt the holder of the Floodplain Use Permit from any additional requirements necessary to obtain flood insurance.
2. The applicant shall provide an Elevation and/or Flood Proofing Certificate prepared by an Arizona Registered Professional Engineer or Land Surveyor to the Floodplain Administrator certifying that the elevation or flood proofing requirement has been met when required. A separate certificate of the appropriate type shall be furnished for each building.
3. The storage or processing of materials that are, in time of flooding, buoyant, flammable, explosive, or could be injurious to human, animal or plant life is prohibited.
4. Storage of other material or equipment may be allowed if approved by the Floodplain Administrator if it will not be subject to major damage by floods and if firmly anchored to prevent flotation, or if readily removable from the area within the time available after flood warning.